About 25 sec into the Demon Form phase, Leotheras summons Inner Demons for up to five raid members (never for the person with aggro). The inner demons can only be attacked by the person to whom they belong. If Leotheras returns to humanoid form while an Inner Demon is still alive, that person becomes Mind Controlled for 10 minutes (non-removable). Pet classes must make sure their pet does not get the killing blow, the Mind Control is only prevented if the player deals the death blow.

Inner Demon capabilities:

~11,000 health

melee damage: ~1000

spell damage: Shadow Bolt for ~3500 (reflectable)

take increased damage (+65%) from arcane,nature, and holy spells

take slightly reduced damage (-20%) from shadow and fire spells

vulnerable to most forms of CC like daze, stun, disorient, fear and even banish (not recommended)

7-8 healers: In the worst case there are 5 inner demons on healers, two healers are absolutely needed for the warlock tank

2-3 tanks: One being warlock, one to two for regaining aggro after whirlwind. Paladins are good for quickly pulling Leotheras back to them with Avenger's Shield after the demon phase. Druid tanks are also good, as they can DPS better during the demon phase and kill their Inner Demon much more easily than a Protection Warrior in tank gear.

14-16 DPS classes. Because of the whirlwind ability, ranged DPS have an easier time than melee.

During a Whirlwind, Leotheras targets his victim. If that person runs away fast and far enough, he will deaggro and whirl towards someone else. It is possible to have ALL raid members avoid being hit. If people are hit by Whirlwind, they must be healed. The DoT part can only be removed with Divine Shield, Blessing of Protection, or Ice Block (Stoneform no longer removes it).

The aggro wipe can be overcome with a hunters Misdirection. Other tricks include having someone place Gnomish Flame Turret/Searing Totem on the tanking spot (Leotheras will aggro this, allowing the MT to get aggro back easily). Bleeds or any other tank DoTs also help them gain aggro immediately when they tick after the aggro wipe. Having a Paladin main tank this encounter is also a good idea because he doesn't have to chase down Leotheras, but can simply throw an Avenger's Shield. Like most raid bosses, Leotheras is immune to taunt.

It's a frequently used tactic to have a demo specced warlock with felhunter and high fire resistance tank this encounter. Nonetheless, it's also possible to tank him conventionally. A combination also works - a normal tank taking the first few attacks can help the warlock tank survive the entire phase.

You need to have about 365 fire resistance and about 18K health raid buffed. Flasks of Chromatic Wonder are great for this. Tank him at the edge of his hitbox to protect melee DPS from being hit by the Chaos Blast splash.

The incoming damage will go from zero (no debuffs) to most of your health bar, but if healers are on the ball you should be able to go up to about 12-14 debuffs before being instagibbed. Thunderclap seems to reduce the frequency of attacks which will make you survive longer.

Threat will probably be a problem, especially when you're not taking damage, so using Mighty Rage Potions is a very good idea and will allow your raid to squeeze out more DPS. High stamina DPS gear will also help assuming you can reach the maximum fire resistance, and use Battle Shout until you have about 4 debuffs then switch to Commanding Shout.

Ask a friendly Paladin to cast Divine Intervention on you during the last 15% if your debuffs stack too high, as this will remove them. Ideally do this when you have a full rage bar to allow you to get him back off healers, and click it off quickly before people start dying.

Whenever a player has to deal with an inner demon, he should be healed by the non-affected healers, even if self healing-capable. DPS classes should find this encounter rather easy. For some classes a few hints may help:

Holy Priest: Simply spamming Smite will effectively kill the Inner Demon with an incredible amount of time left over, almost one of the fastest classes able to kill their demon. Due to the demon taking increased damage from holy, any shadow spells are probably a waste of time. Fearing often causes the demon to run out of DPS range. Any form of healing should not be used except Healthstones, as your priority is to kill your Inner Demon as soon as possible—other healers not Demon'd will take care of you, but feel free to PW:S or Renew before he uses the spell in case you receive it, just waste no time NOT killing your demon. No spell damage gear should be needed.

Restoration Druid: Start with Moonfire, break Tree of Life, then continue with Barkskin, followed by spamming Wrath. Barkskin lasts 12 seconds during that time cast about five Wraths. After that start spamming Moonfire since Wrath gets pushback. Also use Insect Swarm if possible.

Protection Warriors: Warriors should try to be at 100% rage before they can get the demon. This is achieved by simply attacking Leotheras in battle stance in his demon form, economizing on rage as much as possible. When the inner demon is there, spell reflect the demon's shadow bolt. Wear a mix of DPS and tanking gear for this fight.

Hunters: Pets can be used, but that's a little dangerous (lest the pet gets the kill). It's safe to use the pet until about 20%, then put it on passive. If the pet had growl on auto-cast before, it should still hold aggro until the demon is dead. Hunters who can't use their pet (or prefer to leave it on the boss) can use the hunter dance and should be fine too. You can use Freezing Trap also. If you are in melee range and want to get far from your inner demon, freeze him and step back.

Combat Rogues: These have a particularly easy time with inner demons, they can stay on the boss and simply kill the Demon with Blade Flurry.

At 15%, Leotheras' Demon Form splits from his Humanoid Form, and both forms must be handled together. The Demon Form starts with 100% health, while the Humanoid Form retains its current health. The Humanoid Form abilities are the same as before. The Demon Form still uses Chaos Blast, but no longer spawns the Inner Demons. Upon defeating the Humanoid Form, the Demon Form despawns.